Plaskett, John Stanley (1865–1941)
Canadian mechanical engineer and astronomer who, in 1918, became director
of the newly established Dominion Astrophysical
Observatory (DAO) in British Columbia, for which he had organized the
design, construction, and installation of a new 72-inch (1.8-meter) reflecting
telescope. Plaskett's field of research was spectroscopy,
in particular the measurement of radial velocities
of celestial bodies, i.e., their velocities along the line of sight, from
the shift in their spectral lines. Using the 72-inch reflector and a highly
sensitive spectrograph which he had also designed, many spectroscopic
binary systems were discovered. In 1922, Plaskett identified an extremely
massive star as a binary, now known as Plaskett's
Star. In 1927 he provided confirmatory evidence for the theory of galactic
rotation put forward by Bertil Lindblad
and Jan Oort. By 1928 Plaskett, in collaboration
with Joseph Pearce, had obtained evidence
for the hypothesis formulated by Arthur Eddington
in 1926 that interstellar matter was widely distributed throughout the Galaxy;
their disocvery that interstellar absorption lines, mainly of calcium, took
part in the galactic rotation, showed that interstellar matter was not confined
to separate star clusters. Although this result was first announced by Otto
Struve in 1929, Plaskett felt he had priority and was convinced that Struve
had obtained his results from him. He retired from the DAO in 1935.
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